Unescaped field-name regex disables CSFLE in MongoDB C# Driver
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- High · None · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
The MongoDB C# Driver from 3.5.0 before 3.13.0 places caller-supplied field identifiers into a pattern expression in its client-side encryption schema builder without normalizing or validating them, which is CWE-185. An application that designates fields for client-side field-level encryption may have that protection silently fail, so intended-encrypted data is stored and returned in cleartext, and the rule may also apply more broadly than intended. Any party with ordinary read access to the stored data, without the encryption keys, can observe the unprotected values, and no user action is required to trigger the condition.
Written with Claude Haiku 5.5 from the sources below · 2026-10-30
Description from the CNA
A client-side encryption schema construction component in the MongoDB C# Driver places caller-supplied field identifiers into a position that is interpreted as a pattern expression, without normalizing or validating them. As a result, an application that designates certain fields for client-side field-level encryption may have the protection silently fail to apply, so data intended to be encrypted is stored and returned in cleartext; conversely, the rule may apply more broadly than intended. No user action is required to cause the condition, and any party with ordinary read access to the stored data — without possession of the encryption keys — can observe the unprotected values.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
Upgrade MongoDB C# Driver to version 3.13.0 or later, which fixes the flaw.
Written with Claude Haiku 5.5 from the sources below · 2026-10-30
- Fix · CNA C# Driver (MongoDB) Fixed in 3.13.0
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
MongoDB C# Driver 3.13.0
11 records Highest priority Priority HIGH 5 HIGH, 6 MEDIUM
Other records, highest priority first
- TI-2026-79432 BSON output corruption via out-of-range binary subtype in MongoDB C# DriverPriority HIGH 70
- TI-2026-79424 NoSQL command injection via mismatched BSON length in MongoDB C# DriverPriority HIGH 70
- TI-2026-79422 Unbounded memory growth in MongoDB C# Driver BSON deserializationPriority HIGH 69
Timeline
- 2026-10-22 Threatist record created from CVE-2026-114653
- 2026-10-23 1 new reference · CNA
- 2026-10-23 Priority changed: MEDIUM → LOW
- 2026-10-30 CISA SSVC decision points changed
- 2026-10-30 Priority changed: LOW → MEDIUM
References
More MongoDB vulnerabilities
- TI-2019-08023 Code injection in mongo-express KEVCVSS 3.1CRITICAL 9.9
- TI-2025-13542 Zlib compressed protocol header length confusion may allow memory read KEVCVSS 4.0HIGH 8.7
- TI-2026-79432 BSON output corruption via out-of-range binary subtype in MongoDB C# Driver CVSS 4.0MEDIUM 6.9
- TI-2026-79424 NoSQL command injection via mismatched BSON length in MongoDB C# Driver CVSS 4.0MEDIUM 6.9
- TI-2026-79422 Unbounded memory growth in MongoDB C# Driver BSON deserialization CVSS 4.0HIGH 8.2
- TI-2026-79427 Authentication bypass via issuer-and-serial-only certificate equality CVSS 4.0HIGH 7.6
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences